Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J4/00—Measuring polarisation of light
  • G01J4/04—Polarimeters using electric detection means
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
  • A61B5/0062—Arrangements for scanning
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/21—Polarisation-affecting properties
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
  • A61B5/0062—Arrangements for scanning
  • A61B5/0064—Body surface scanning
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/44—Detecting, measuring or recording for evaluating the integumentary system, e.g. skin, hair or nails
  • A61B5/441—Skin evaluation, e.g. for skin disorder diagnosis
  • A61B5/442—Evaluating skin mechanical properties, e.g. elasticity, hardness, texture, wrinkle assessment
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/8422—Investigating thin films, e.g. matrix isolation method
  • G01N2021/8438—Mutilayers

Definitions

• the present invention relates to a device and a method for determining a polarization information at a point of a target sample, as well as a polarimetric imager.
• the invention relates to a type determination device comprising:
• a light source capable of emitting a linearly polarized light beam in a predefined direction, the light beam being intended to be reflected by the measurement point of the target sample;
• a polarization information determining device makes it possible to obtain information on the micro or nanostructuration of target samples, on their texture on the surface or at shallow depth below the surface.
• This polarization information may be, for example, the phase shift experienced or the degree of polarization of the beam returned by the target sample.
• This information is mainly used in the medical field for the diagnosis of diseases, and in the field of microelectronics to characterize thin films monolayer, multilayer or to analyze complex surfaces.
• the polarization information is obtained by reflection of a polarized light beam on a target sample.
• the analysis of the polarization of the reflected beam makes it possible to determine polarization information of the target sample.
• the object of the invention is in particular to overcome this drawback and to propose a device for determining a polarization information that allows, among other things, to analyze non-accessible target samples by a direct-sighted light beam.
• the subject of the invention is a device for determining the aforementioned type, characterized in that it comprises: at least one waveguide able to guide the incident beam towards the target sample, and the reflected beam towards the means of calculation; and
• Polarization rotation means adapted to rotate two orthogonal polarimetric components Ey 1 ; E ⁇ 1 of the incident beam after passage in the waveguide and two orthogonal polarimetric components E
• This invention makes it possible to analyze biological tissue structures such as collagen, in vivo, in situ and without the need for a biopsy.
• the invention also relates to a polarimetric imager capable of generating a polarimetric image of a target sample, said imager comprising:
• a device for determining polarization information as described above said device being able to determine a plurality of polarization information; a unit for constructing a polarimetric image representative of the polarization information of the measurement points of the target sample, each characteristic of a pixel of the image representing the polarization information of a measuring point of the target sample.
• the subject of the invention is also a method for determining a polarization information at a measurement point of a target sample, said method comprising the following steps: a) a step of emitting an incident light beam polarized rectilinearly in a predefined direction; b) a step of guiding the incident beam towards the measurement point of the target sample using a waveguide; c) a step of rotating two orthogonal polarimetric components of the incident beam after passing through the waveguide; d) a step of reflection of the incident beam on the measurement point of the target sample; e) a step of rotating two orthogonal polarimetric components of the reflected beam before passing through the waveguide; f) a step of guiding the beam reflected to a computing unit by the same waveguide; g) a step of calculating the polarization information of the measurement point of the target sample from the reflected beam recovered at the output of the waveguide; steps c) and e) compensate for the effect of birefringence of the waveguide
• FIG. 1 is a schematic view of the determination device according to the invention
• FIG. 2 is a graph showing the time evolution of the perpendicular polarimetric component of the electric field as a function of the parallel polarimetric component
• Figures 3 to 6 are schematic views of a polarimetric imager according to four embodiments of the invention
• - Figure 7 is a diagram of the steps of the method according to the invention.
• the determination device 2 comprises a monochromatic light source 4 capable of emitting an incident light beam, a waveguide 6 adapted to be traversed by an incident beam and by a beam reflected by the target sample. 8, and means 9 for calculating the polarization information from the reflected beam recovered at the output of the waveguide 6.
• the light beam is called “incident beam” over the entire path from source 4 to the target sample 8, and “reflected beam” over the entire path of the target sample 8 to the calculation means 9.
• the terms “upstream” and “downstream” are defined according to the direction of the light beam.
• the light source 4 is able to emit an incident light beam polarized rectilinearly in a predefined direction x.
• This light source 4 is, for example, constituted by a laser diode 10, a polarizer 12 and a half-wave plate 14.
• the polarizer 12 and the half-wave plate 14 are arranged downstream of the laser diode, considering the direction of the incident beam. They are adapted to be traversed by the beam emitted by the laser diode 10.
• the light source 4 may include a device for protecting it from external reflections.
• the determination device 2 comprises between the light source 4 and the waveguide 6, a cube 16 beam splitter and a system 18 for focusing the incident beam in the waveguide 6.
• the cube 16 is neutral to the polarization. It affects only the intensity of the beam coming from the light source 4 and going towards the waveguide 6. It is capable of modifying the direction of the reflected beam in order to direct it towards the calculation means 9.
• the focusing system 18 is constituted for example by a microscope objective or a convergent lens whose focal plane is located at the entrance of the waveguide 6.
• the waveguide 6 is adapted to guide the incident beam on the target sample 8, in particular when the latter is positioned in a cavity or a recess, or even in the human body, so that it can not be achieved by transmission of a light beam in direct sight. It has an end 6a called said proximal end, located near the light source 4 and calculation means 9, and a distal end 6b said end intended to be disposed near the target sample 8.
• the waveguide 6 is constituted by a monomode optical fiber at the wavelength of the beam emitted by the light source 4.
• Means 19 for varying the birefringence of the waveguide 6 are mounted on the waveguide 6. These means 19 have the effect of varying the polarization of the beam passing through the waveguide. These variation means 19 comprise, for example, means adapted to vibrate the waveguide 6, means capable of generating a field electrical or means able to vary the temperature or the pressure exerted on it, so as to vary temporally the polarization of the beam output of the waveguide 6.
• the variation means 19 are connected to the calculation means 9 and are controlled by them.
• the crossing of the waveguide 6 modifies the incident beam so that, at the output of the waveguide 6, it has two orthogonal polarimetric components Ey 1 and E 2
• the device of FIG. determination 2 comprises, considering the direction of the incident beam, a first optical system 20 whose focal plane is located at the opening of the distal end of the waveguide 6, polarization rotation means 22, and a second optical system 24 whose focal plane is located at the target sample 8.
• the first optical system 20 is able to collimate the incident beam.
• the second optical system 24 is able to focus the incident beam on the measurement point of the target sample.
• the reflected beam After reflection on the target sample 8, the reflected beam is collimated by the second optical system 24, it passes through the rotation means 22 and is focused by the first optical system 20 at the entrance of the distal portion 6b of the guide. 'wave.
• the rotation means 22 comprise a Faraday rotator. For medical applications, this rotator is miniaturized.
• the Faraday rotator After reflection of the incident beam on the target sample 8, the Faraday rotator is able to rotate two orthogonal polarimetric components of the beam Reflected referenced Ey R and Ej_ R at an angle of 45 degrees in the same direction of rotation to obtain two orthogonal polarimetric components referenced and
• the polarimetric components Ey IR and Ej_ IR of the incident beam downstream of the rotation means 22 are different from the polarimetric components E
• the downstream term is defined considering the direction of the incident beam.
• the term upstream is defined by considering the direction of the reflected beam.
• the waveguide 6 is adapted to guide the reflected beam towards the focusing system 18.
• the determination device 2 comprises in in addition to a cube 26 polarization separator and two photodetectors 28, 30 connected to the calculation means 9.
• the cube 26 is shaped to separate a polarimetric component Ey F oriented in the predefined direction x, that is to say in the direction in which the light source 4 has polarized the incident beam, and a polarimetric component Ej_ F orthogonal to that -this.
• F and the orthogonal polarimetric component Ej- F of the reflected beam are respectively directed towards the photodetector 28, and towards the photodetector 30.
• the photodetectors 28, 30 each deliver a photocurrent, hereinafter referred to as an electrical signal, to the calculation means 9.
• F and Ej / vary over time due to the polarization variations generated by the variation means 19.
• F is shown in Figure 2 for a target sample having a phase shift of 90 degrees between its own axes.
• the calculation means 9 are suitable for selecting the maximum value of the electrical signal representative of the parallel polarimetric component E
• the calculation means 9 are also adapted to select the minimum value of the electrical signal representative of the parallel polarimetric component E
• the maximum parallel polarimetric component is the polarimetric component Ep F.
• mm is the minimum power obtained from the minimum value of the electrical signal selected by the calculation means 9. It is representative of the parallel polarimetric component E
• P_ ⁇ _ max is the representative power of the perpendicular polarimetric component Ej_ F of the electric field measured at the same time.
• mm) is the total power recovered by the photodetectors 28 and 30.
• the calculation means 9 are also adapted to calculate the phase shift ⁇ introduced between the proper axes of the target sample from the following formula: s in 2 A _ (î - ⁇ ). p // mSiX - ⁇ . p ⁇ mm
• max is the maximum power obtained from the maximum value of the electrical signal selected by the calculation means 9. It is representative of the parallel polarimetric component Ey F of the electric field.
• the calculation means 9 are suitable for selecting the average value of the electric signal representative of the parallel polarimetric component Ey F as well as the corresponding value of the electrical signal representative of the perpendicular polarimetric component Ej_ F measured at the same time.
• - f is a continuously increasing function between 0 and 180 ° when x varies from 0 to 1.
• the waveguide 6 is a multimode optical fiber.
• FIG. 3 represents a polarimetric imager 32 according to a first embodiment of the invention.
• the imager 32 is formed from a device 2 for determining a polarization information, as described above, equipped with a unit 34 for building a polarimetric image and a scanning system 36.
• the building unit 34 is adapted to receive the values of the degree of polarization of the beam and the phase shift values from several measurement points of the target sample 8 and to construct two polarimetric images therefrom.
• Each gray level or each chrominance of a pixel in the first image represents the degree of polarization associated with a measurement point of the target sample.
• Each gray level or each chrominance of a pixel in the second image represents the phase shift at a measurement point of the target sample.
• the image building unit 34 is synchronized with the scanning system 36.
• the scanning system 36 is capable of directing the incident beam towards several measurement points of the target sample 8.
• It is disposed downstream of the waveguide 6 by considering the direction of travel of the incident beam. In particular, it is disposed between the distal end 6b of the waveguide and the first optical system 20.
• FIG. 4 represents a polarimetric imager 32 according to a second embodiment of the invention. It is similar to the imager shown in Figure 3.
• the waveguide 6 is replaced by several waveguides 40, or by a multicore optical fiber, and the scanning system 36 is arranged upstream of the waveguides by considering the direction of the incident beam.
• the scanning system 36 is adapted to direct the incident beam in turn towards each waveguide so that the beam sequentially illuminates a plurality of measurement points of the target sample 8.
• the scanning system sequentially processes the reflected beam.
• the building unit 34 is synchronized with the scanning system 36 so as to be able to assign to each polarization information calculated by the calculation unit 9 a corresponding position on the target sample 8.
• FIG. 5 represents a polarimetric imager 32 according to a third embodiment of the invention. It is similar to the imager shown in FIG. 4. However, the means 19 for varying the birefringence are replaced by polarization variation means 42 mounted between the cube 16 and the scanning system 36.
• the means 42 of FIG. variation of the polarization are constituted, for example, by a polarization jammer or an arrangement of phase blades controlled by the calculation unit 9.
• the means 42 for varying the polarization can also be used (instead of the means 19 for varying the birefringence) in the determination device illustrated in FIG. 1, as well as in the imagers illustrated in FIGS. 2 to 4.
• FIG. 6 represents a polarimetric imager 32 according to a fourth embodiment of the invention. It is similar to the imager shown in Figure 5. However, the monochromatic light source has been replaced by a polychromatic source
• the polychromatic source is, for example, constituted by a superluminescent diode. Since the birefringence of the waveguides varies as a function of the wavelength of the beam passing through them, the variation of polarization previously achieved by the variation means 19 or 42 is here induced by the passage in the waveguides of the waveguides. a broad spectrum beam.
• the calculation means 9 are suitable for selecting the maximum value and the minimum value of the electric signal representative of the parallel polarimetric component Ey F among the components of the electric field having different wavelengths.
• the value of the polarimetric component perpendicular E_ F L having the same wavelength is selected for calculating the degree of polarization and phase.
• the invention also relates to a method for determining a polarization information illustrated in FIG. 7.
• the method starts with a step 46 for emitting a linearly polarized incident light beam.
• the incident beam is guided towards the measurement point of the target sample using the waveguide 6.
• a step 50 two orthogonal polarimetric components of the incident beam are rotated at a 45 degree angle by the Faraday rotator 22.
• the incident beam is retro-reflected on the measurement point of the target sample.
• a step 54 two orthogonal polarimetric components of the reflected beam are rotated at an angle of 45 degrees. Then, the reflected beam is injected into the waveguide 6 by the optical system 20. During a step 56, the reflected beam is guided to the computing unit 9 by the same waveguide 6.
• the polarization information of the measurement point of the target sample is calculated from the reflected beam recovered at the exit of the waveguide 6.
• the phase shift provides, for example, information on the birefringence of the target sample while the degree of polarization provides information on its ability to depolarize light.
• the determination device 2 in which the polarimetric imager 32 comprises a first rotator disposed solely on the path of the incident beam between the distal portion 6b and the target sample 8, and a second rotator arranged solely on the path of the reflected beam. between the distal portion 6b and the target sample 8.
• the first rotator is capable of rotating the polarimetric components of the beam by an angle ⁇ .
• the second rotator is capable of rotating the polarimetric components by a 90- ⁇ degree angle; ⁇ being between 0 and 90 degrees.
• the incident beam is not perpendicular to the surface of the target sample.

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• 2009
  • 2009-01-15 FR FR0950236A patent/FR2941047A1/fr active Pending
  • 2009-01-28 FR FR0950535A patent/FR2941048B1/fr not_active Expired - Fee Related
  • 2009-05-20 FR FR0953402A patent/FR2941045B1/fr not_active Expired - Fee Related
• 2010
  • 2010-01-15 ES ES10706703T patent/ES2896280T3/es active Active
  • 2010-01-15 EP EP10706703.5A patent/EP2376882B1/de active Active
  • 2010-01-15 EP EP10706023A patent/EP2376881A1/de not_active Withdrawn
  • 2010-01-15 WO PCT/FR2010/050064 patent/WO2010082000A1/fr not_active Ceased
  • 2010-01-15 WO PCT/FR2010/050063 patent/WO2010081999A1/fr not_active Ceased
  • 2010-01-15 US US13/144,519 patent/US8896833B2/en active Active
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